19-4759; Rev 1; 1/99 L MANUA ION KIT HEET T A U L EVA TA S WS DA FOLLO 1-Cell to 3-Cell, High-Power (1A), Low-Noise, Step-Up DC-DC Converters Features The MAX1700/MAX1701 are high-efficiency, low-noise, step-up DC-DC converters intended for use in batterypowered wireless applications. They use a synchronous-rectified pulse-width-modulation (PWM) boost topology to generate 2.5V to 5.5V outputs from battery inputs such as one to three NiCd/NiMH cells or one LiIon cell. Both devices have an internal 1A, 130mΩ Nchannel MOSFET switch and a 250mΩ P-channel synchronous rectifier. ♦ Up to 96% Efficiency With their internal synchronous rectifier, the MAX1700/ MAX1701 deliver 5% better efficiency than similar nonsynchronous converters. They also feature a pulsefrequency-modulation (PFM) standby mode to improve efficiency at light loads, and a 3µA shutdown mode. ♦ External Clock or Internal 300kHz Oscillator The MAX1700/MAX1701 come in 16-pin QSOP packages (which occupy the same space as an 8-pin SO). The MAX1701 includes two comparators to generate power-good and low-battery warning outputs. It also contains a gain block that can be used to build a linear regulator using an external P-channel pass device. For higher-power outputs, refer to the MAX1703. For dual outputs (step-up and linear regulator), refer to the MAX1705/MAX1706. For an on-board analog-to-digital converter, refer to the MAX848/MAX849. ♦ 1.1 VIN Guaranteed Start-Up ♦ 0.7V to 5.5V Input Range ♦ Up to 800mA Output ♦ Step-Up Output (adjustable from 2.5V to 5.5V) ♦ PWM/PFM Synchronous-Rectified Topology ♦ 3µA Logic-Controlled Shutdown ♦ Power-Good Output (MAX1701) ♦ Low-Battery Comparator (MAX1701) ♦ Uncommitted Gain Block (MAX1701) Ordering Information PART MAX1700EEE MAX1701EEE TEMP. RANGE PIN-PACKAGE -40°C to +85°C -40°C to +85°C 16 QSOP 16 QSOP The MAX1701 evaluation kit is available to speed design time. Typical Operating Circuit Applications Digital Cordless Phones PCS Phones Personal Communicators Palmtop Computers Wireless Handsets Two-Way Pagers Hand-Held Instruments INPUT 0.7V TO 5.5V Pin Configurations MAX1700 ON TOP VIEW I.C. 1 16 I.C. I.C. 2 15 POUT REF 3 14 OUT CLK/SEL 4 MAX1700 OUTPUT 3.3V OR ADJ UP TO 800mA OFF ONA ON ONB LX OFF PWM PFM OR SYNC CLK/SEL POUT 13 LX 12 PGND GND 5 I.C. 6 11 FB REF ONB 7 10 I.C. FB ONA 8 9 OUT GND PGND I.C. QSOP I.C. = INTERNAL CONNECTION. LEAVE OPEN OR CONNECT TO GND Pin Configurations continued at end of data sheet. ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. MAX1700/MAX1701 General Description MAX1700/MAX1701 1-Cell to 3-Cell, High-Power (1A), Low-Noise, Step-Up DC-DC Converters ABSOLUTE MAXIMUM RATINGS ONA, ONB, OUT, AO, POK, LBO to GND...................-0.3V, +6V PGND to GND.....................................................................±0.3V LX to PGND.....................................................-0.3V,VPOUT+0.3V CLK/SEL, AIN, REF, FB, LBP, LBN, POUT to GND............-0.3V, VOUT+0.3V ................................................................................... Continuous Power Dissipation (TA=+70°C) 16-QSOP (Derate 8.30mW/°C above +70°C) ...............667mW Operating Temperature Ranges MAX1700EEE, MAX1701EEE ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +160°C Lead Temperature (soldering, 10sec) .............................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (CLK/SEL = ONA = ONB = FB = PGND = GND, OUT = POUT, VOUT = 3.6V (Note 6); MAX1701: AIN = LBN = GND, LBP = REF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS MIN TYP MAX UNITS 0.7 5.5 V 0.9 1.1 V DC-DC CONVERTER Input Voltage Range (Note 1) Minimum Start-Up Voltage (Note 2) ILOAD < 1mA, TA = +25°C Frequency in Start-Up Mode VOUT = 1.5V 40 150 300 kHz Output Voltage (Note 3) VFB < 0.1V, CLK/SEL = OUT, VBATT = 2.4V, includes load regulation error for 0A ≤ ILX ≤ 0.55A 3.17 3.30 3.38 V FB Regulation Voltage Adjustable output, CLK/SEL = OUT, VBATT = 2.4V, includes load regulation error for 0A ≤ ILX ≤ 0.55A 1.210 1.24 1.255 V FB Input Current VFB = 1.25V 0.01 Output Voltage Adjust Range 2.5 Output Voltage Lockout Threshold (Note 4) Load Regulation (Note 5) CLK/SEL = OUT, No load to full load 2.0 2.15 20 nA 5.5 V 2.3 V -1.6 % MAX1700 0.1 20 MAX1701 3 20 Supply Current in Shutdown V ONB = 3.6V µA Supply Current in Low-Power Mode (Note 6) CLK/SEL = GND (MAX1700) 35 70 CLK/SEL = GND (MAX1701) 55 110 Supply Current in Low-Noise Mode (Note 6) CLK/SEL = OUT (MAX1700) 125 250 CLK/SEL = OUT (MAX1701) 140 300 POUT Leakage Current VLX = 0V, VOUT = 5.5V 0.1 20 µA LX Leakage Current VLX = V ONB = VOUT = 5.5V 0.1 20 µA CLK/SEL = GND 0.2 0.45 CLK/SEL = OUT 0.13 0.28 0.25 0.5 µA µA DC-DC SWITCHES Switch On-Resistance N-channel P-channel N-Channel Current Limit P-Channel Turn-Off Current 2 CLK/SEL = OUT 1100 1300 1600 CLK/SEL = GND 250 400 550 CLK/SEL = GND 20 _______________________________________________________________________________________ 120 Ω mA mA 1-Cell to 3-Cell, High-Power (1A), Low-Noise, Step-Up DC-DC Converters (CLK/SEL = ONA = ONB = FB = PGND = GND, OUT = POUT, VOUT = 3.6V (Note 6); MAX1701: AIN = LBN = GND, LBP = REF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS MIN TYP MAX UNITS 1.25 1.263 V 30 nA 9 16 mmho GAIN BLOCK (MAX1701) AIN Reference Voltage IAO = 20µA 1.237 AIN Input Current VAIN = 1.5V -30 Transconductance 10µA < IAO = 100µA AO Output Low Voltage VAIN = 0.7V, IAO = 100µA 0.1 0.4 V AO Output High Leakage VAIN = 1.5V, VAO = 5.5V 0.01 1 µA 5 POWER GOOD (MAX1701) Internal Trip Level Rising VOUT, VFB < 0.1V 2.93 2.97 3.02 V External Trip Level Rising VFB 1.1 1.12 1.14 V POK Low Voltage ISINK = 1mA, VOUT = 3.6V or ISINK = 20µA, VOUT = 1V 0.03 0.4 V POK High Leakage Current VOUT = VPOK = 5.5V 0.01 1 µA ±0.5 5 mV 1.5 V LOW-BATTERY COMPARATOR LBN, LBP Input Offset LBP falling, 15mV hysteresis -5 LBN, LBP Common Mode Range To maintain input offset < ±5mV (at least one input must be within this range) 0.5 LBO Output Low Voltage ISINK = 1mA, VOUT = 3.6V or ISINK = 20µA, VOUT = 1V 0.03 0.4 V LBO High Leakage VOUT = VLBO = 5V 0.01 1 µA LBN, LBP Input Current VLBP = VLBN = 1.5V 20 nA 1.250 1.263 V 5 15 mV 0.2 5 mV REFERENCE Reference Output Voltage IREF = 0 REF Load Regulation -1µA < IREF < 50µA REF Supply Rejection 2.5V < VOUT < 5V 1.237 LOGIC AND CONTROL INPUTS Input Low Voltage (Note 7) 1.2V < VOUT < 5.5V, ONA and ONB 0.2VOUT 2.5V < VOUT < 5.5V, CLK/SEL 0.2VOUT Input High Voltage (Note 7) Input High Voltage (Note 7) 1.2V < VOUT < 5.5V, ONA and ONB 0.8VOUT 2.5V < VOUT < 5.5V, CLK/SEL 0.8VOUT Logic Input Current ONA, ONB, and CLK/SEL Internal Oscillator Frequency CLK/SEL = OUT V V 1 µA 260 -1 300 340 kHz Oscillator Maximum Duty Cycle 80 86 90 % External Clock Frequency Range 200 400 kHz Minimum CLK/SEL Pulse Width 200 ns Maximum CLK/SEL Rise/Fall Time 100 ns _______________________________________________________________________________________ 3 MAX1700/MAX1701 ELECTRICAL CHARACTERISTICS (continued) MAX1700/MAX1701 1-Cell to 3-Cell, High-Power (1A), Low-Noise, Step-Up DC-DC Converters ELECTRICAL CHARACTERISTICS (continued) (CLK/SEL = ONA = ONB = FB = PGND = GND, OUT = POUT, VOUT = 3.6V (Note 6); MAX1701: AIN = LBN = GND, LBP = REF, TA = -40°C to +85°C, unless otherwise noted.) (Note 8) PARAMETER CONDITIONS MIN Output Voltage (Note 3) VFB < 0.1V, CLK/SEL = OUT, VBATT = 2.4V, includes load regulation error for 0A ≤ ILX ≤ 0.55A FB Regulation Voltage TYP MAX UNITS 3.17 3.38 V Adjustable output, CLK/SEL = OUT, VBATT = 2.4V, includes load regulation error for 0A ≤ ILX ≤ 0.55A 1.20 1.27 V Output Voltage Lockout Threshold (Note 4) 2.0 2.3 V Supply Current in Shutdown V ONB = 3.6V 20 µA Supply Current in Low-Power Mode (Note 6) CLK/SEL = GND (MAX1700) 70 CLK/SEL = GND (MAX1701) 110 Supply Current in Low-Noise Mode (Note 6) CLK/SEL = OUT (MAX1700) 250 CLK/SEL = OUT (MAX1701) 300 DC-DC CONVERTER µA µA DC-DC SWITCHES Switch On-Resistance N-channel CLK/SEL = GND 0.45 CLK/SEL = OUT 0.28 P-channel Ω 0.5 CLK/SEL = OUT 1100 1800 CLK/SEL = GND 250 600 AIN Reference Voltage IAO = 20µA 1.23 1.27 V Transconductance 10µA < IAO < 100µA 5 16 mmho N-Channel Current Limit mA GAIN BLOCK (MAX1701) POWER-GOOD (MAX1701) Internal Trip Level Rising VOUT, VFB < 0.1V 2.92 3.03 V External Trip Level Rising VFB 1.1 1.14 V LOW-BATTERY COMPARATOR (MAX1701) LBN, LBP Input Offset LBP falling, 15mV hysteresis -5 5 mV LBN, LBP Common Mode Range To maintain input offset < ±5mV (at least one input must be within this range) 0.5 1.5 V IREF = 0 1.23 1.27 V REFERENCE Reference Output Voltage 4 _______________________________________________________________________________________ 1-Cell to 3-Cell, High-Power (1A), Low-Noise, Step-Up DC-DC Converters (CLK/SEL = ONA = ONB = FB = PGND = GND, OUT = POUT, V OUT = 3.6V, MAX1701: AIN = LBN = GND, LBP = REF, TA = -40°C to +85°C, unless otherwise noted.) (Note 8) PARAMETER CONDITIONS MIN TYP MAX UNITS LOGIC AND CONTROL INPUTS Input Low Voltage (Note 7) Input High Voltage (Note 7) Input High Voltage (Note 7) 1.2V < VOUT < 5.5V, ONA and ONB 0.2VOUT 2.5V < VOUT < 5.5V, CLK/SEL 0.2VOUT 1.2V < VOUT < 5.5V, ONA and ONB 0.8VOUT 2.5V < VOUT < 5.5V, CLK/SEL 0.8VOUT Logic Input Current ONA, ONB, and CLK/SEL Internal Oscillator Frequency CLK/SEL = OUT V V -1 1 µA 260 340 kHz Oscillator Maximum Duty Cycle 80 92 % External Clock Frequency Range 200 400 kHz Note 1: Operating voltage. Since the regulator is bootstrapped to the output, once started it will operate down to 0.7V input. Note 2: Start-up is tested with the circuit of Figure 2. Note 3: In low-power mode (CLK/SEL = GND), the output voltage regulates 1% higher than low-noise mode (CLK/SEL = OUT or synchronized). Note 4: The regulator is in start-up mode until this voltage is reached. Do not apply full load current. Note 5: Load regulation is measured from no-load to full load where full load is determined by the N-channel switch current limit. Note 6: Supply current from the 3.30V output is measured between the 3.30V output and the OUT pin. This current correlates directly to the actual battery supply current, but is reduced in value according to the step-up ratio and efficiency. Set VOUT = 3.6V to keep the internal switch open when measuring the current into the device. Note 7: ONA and ONB have hysteresis of approximately 0.15xVOUT. Note 8: Specifications to -40°C are guaranteed by design and not production tested. Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) 60 VIN = 0.9V VIN = 2.4V 80 70 VIN = 1.2V 60 50 50 PFM PWM 40 PFM PWM 0.1 1 10 100 LOAD CURRENT (mA) 1000 T = 25°C 5.0 4.0 T = 85°C 3.0 T = -40°C 2.0 1.0 30 40 6.0 MAX1770-03 90 SHUTDOWN CURRENT (µA) VIN = 1.2V 70 VIN = 3.6V EFFICIENCY (%) EFFICIENCY (%) 80 7.0 MAX1700-02 VIN = 2.4V 90 100 MAX1700-01 100 MAX1701 SHUTDOWN CURRENT vs. INPUT VOLTAGE (V) EFFICIENCY vs. LOAD CURRENT (VOUT = 5V) EFFICIENCY vs. LOAD CURRENT (VOUT = 3.3V) 0 0.1 1 10 100 LOAD CURRENT (mA) 1000 0 1 2 3 4 5 6 INPUT VOLTAGE (V) _______________________________________________________________________________________ 5 MAX1700/MAX1701 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) REFERENCE VOLTAGE vs. REFERENCE CURRENT FREQUENCY vs. TEMPERATURE 1.248 1.250 1.248 1.246 1.246 1.244 1.244 VOUT = 5V 315 FREQUENCY (kHz) 1.250 320 1.252 REFERENCE VOLTAGE (V) 1.252 325 MAX1700-05 1.254 MAX1700-04 1.254 MAX1700-06 REFERENCE VOLTAGE vs. TEMPERATURE REFERENCE VOLTAGE (V) 310 305 300 295 VOUT = 3.3V 290 285 -40 -20 0 20 40 60 80 100 280 0 10 TEMPERATURE (°C) 20 30 40 50 60 70 80 1.5 1.3 1.1 TA = -40°C 0.9 60 80 100 120 140 MAX1700-08 PWM 1.2 1.0 0.8 0.6 TA = +25°C 0.7 40 1.4 CURRENT LIMIT (A) 1.7 20 TEMPERATURE (°C) 1.6 MAX1700/01 TOC06a NO-LOAD START-UP: 1.0V AT -40°C 0.79 AT +25°C 0.64V AT +85°C CONSTANT-CURRENT LOAD VOUT = 3.3V L = 10µH D1 = MBR0520L 1.9 0 PEAK INDUCTOR CURRENT vs. OUTPUT VOLTAGE 2.3 2.1 -40 -20 REFERENCE CURRENT (µA) START-UP INPUT VOLTAGE vs. OUTPUT CURRENT START-UP INPUT VOLTAGE (V) MAX1700/MAX1701 1-Cell to 3-Cell, High-Power (1A), Low-Noise, Step-Up DC-DC Converters 0.4 PFM TA = +85°C 0.5 0.2 0.01 0.1 1 10 1000 100 2.5 OUTPUT CURRENT (mA) 3 3.5 4 4.5 5 5.5 OUTPUT VOLTAGE (V) HEAVY-LOAD SWITCHING WAVEFORMS (VOUT = 3.3V) LINE-TRANSIENT RESPONSE MAX1700-08 MAX1700-09 VOUT A 0V A B 0V 0A B C 1µs/div 6 5ms/div VIN = 1.1V, IOUT = 200mA, VOUT = 3.3V IOUT = 0mA, VOUT = 3.3V A = LX VOLTAGE, 2V/div B = INDUCTOR CURRENT, 0.5A/div C = VOUT RIPPLE, 50mV/div, AC COUPLED A = VIN, 1.1V TO 2.1V, 1V/div B = VOUT RIPPLE, 50mV/div, AC COUPLED _______________________________________________________________________________________ 1-Cell to 3-Cell, High-Power (1A), Low-Noise, Step-Up DC-DC Converters POWER-ON DELAY (PFM MODE) LOAD-TRANSIENT RESPONSE MAX1700-10 MAX1700-11 3.3V A 200mA A 0A B C B 0mA 5ms/div 2ms/div A = VON1, 2V/div B = VOUT, 1V/div C = INPUT CURRENT, 0.2A/div VIN = 1.1V, VOUT = 3.3V A = LOAD CURRENT, 0mA TO 200mA, 0.2A/div B = VOUT RIPPLE, 50mV/div, AC COUPLED DECT LOAD-TRANSIENT RESPONSE GSM LOAD-TRANSIENT RESPONSE MAX1700-13 MAX1700-12 3.3V 5V A A B B 0A 0A 2ms/div 1ms/div VIN = 3.6V, VOUT = 5V, COUT = 440µF VIN = 1.2V, VOUT = 3.3V, COUT = 440µF A = VOUT RIPPLE, 200mV/div, AC COUPLED B = LOAD CURRENT, 100mA TO 1A, 0.5A/div, PULSE WIDTH = 577µs A = VOUT RIPPLE, 200mV/div, AC COUPLED B = LOAD CURRENT, 50mA TO 400mA, 0.2A/div, PULSE WIDTH = 416µs NOISE SPECTRUM (VOUT = 3.3V, VIN = 1.2V, RLOAD = 50Ω) NOISE (mVRMS) MAX1700-14 2.7 0 0.1k 1k 10k FREQUENCY (Hz) 100k 1M _______________________________________________________________________________________ 7 MAX1700/MAX1701 Typical Operating Characteristics (continued) (Circuit of Figure 1, TA = +25°C, unless otherwise noted.) 1-Cell to 3-Cell, High-Power (1A), Low-Noise, Step-Up DC-DC Converters MAX1700/MAX1701 Pin Description PIN 8 NAME FUNCTION MAX1700 MAX1701 — 1 LBP Low-Battery Comparator Non-Inverting Input — 2 LBN Low-Battery Comparator Inverting Input 3 3 REF Reference Output. Bypass with a 0.22µF capacitor to GND. REF can source up to 50µA. Switching-Mode Selection and External-Clock Synchronization Inputs. • CLK/SEL=Low: Low-power, delivers up to 10% of full load current. • CLK/SEL=High: High-power PWM mode. Full output power available. Operates in low-noise, constant-frequency mode. • CLK/SEL=External Clock: High-power PWM mode with the internal oscillator synchronized to the external clock. Turning on with CLK/SEL=0V also serves as a soft-start function since peak inductor current is limited to 25% of that allowed in PWM mode. 4 4 CLK/SEL 5 5 GND Ground — 6 POK Power-Okay Comparator Output. Open drain N-channel output is low when VOUT is 10% below regulation point. No internal delay is provided. 7 7 ONB Shutdown Input. When ONB =high and ONA=low, the IC is off and the load is connected to the battery through the Schottky diode. Turn ON Input. When ONA=high or ONB =low, the IC turns on. 8 8 ONA — 9 AO Gain Block Output. This open-drain output sinks when VAIN <VREF. — 10 AIN Gain Block AIN input. When AIN is low, AO sinks current. The transconductance from AIN to AO is 9mmhos. 11 11 FB DC-DC Converter Dual-Mode Feedback Input. For a fixed output voltage of +3.3V, connect FB to GND. For adjustable output, connect a divider between POUT and GND to set the output voltage in the range of 2.5V to 5V. 12 12 PGND 13 13 LX 14 14 OUT 15 15 POUT — 16 LBO Low-Battery Comparator Output. Open-drain N-channel output is low when LBN > LBP Input hysteresis is 15mV. 1, 2, 6, 9, 10, 16 — I.C. Internal Connection. Leave open or connect to GND. Source of N-Channel Power MOSFET Switch. Connect to high-current ground path. Drain of P-Channel Synchronous Rectifier and N-Channel Switch Output Sense Input. Power source for the IC. Source of P-Channel Synchronous Rectifier MOSFET Switch. Connect an external Schottky diode from LX to POUT. _______________________________________________________________________________________ 1-Cell to 3-Cell, High-Power (1A), Low-Noise, Step-Up DC-DC Converters MAX1700/MAX1701 UNDERVOLTAGE LOCKOUT OUT IC PWR PFM/PWM CONTROLLER 2.25V START-UP EN OSCILLATOR Q D Q POUT PCH 0.25Ω ONA ON ONB REF 1.25V RDY OSCILLATOR 300kHz FEEDBACK AND POWER-GOOD SELECT FB OSC EN REF GND CLK/SEL LX EN REFERENCE FEEDBACK Q PFM/PWM NCH 0.13Ω MODE PGND POK* FB N AIN* AO* GAIN BLOCK N REF COMPARATOR LBP* LBO* N LBN* *MAX1701 ONLY Figure 1. Functional Diagram _______________Detailed Description The MAX1700/MAX1701 are highly efficient, low-noise power supplies for portable RF and data acquisition instruments. The MAX1700 combines a boost switching regulator, N-channel power MOSFET, P-channel synchronous rectifier, precision reference, and shutdown control. The MAX1701 contains all of the MAX1700 features plus a versatile gain amplifier, POK output, and a low-battery comparator (Figure 1). The MAX1700/ MAX1701 come in a 16-pin QSOP package, which occupies no more space than an 8-pin SO. The switching DC-DC converter boosts a 1- to 3-cell input to an adjustable output between 2.5V and 5.5V. The MAX1700/MAX1701 start from a low 1.1V input and remain operational down to 0.7V. These devices are optimized for use in cellular phones and other applications requiring low noise during full- power operation, as well as low-quiescent current for maximum battery life during standby and shutdown modes. They feature constant-frequency (300kHz), lownoise PWM operation with up to 800mA output capability. See Table 1 for typical available output current. A low-quiescent-current, low-power mode offers an output up to 100mA and reduces quiescent power consumption to 200µW. In shutdown mode, the quiescent current is further reduced to just 3µA. Figure 2 shows the standard application circuit for the MAX1700/MAX1701. Additional features include synchronous rectification for high efficiency and improved battery life, a POK output, and an uncommitted comparator for low-battery detection (MAX1701). A CLK input allows frequency synchronization to reduce interference. Dual shutdown controls allow shutdown using a momentary pushbutton switch and microprocessor control (MAX1701). _______________________________________________________________________________________ 9 MAX1700/MAX1701 1-Cell to 3-Cell, High-Power (1A), Low-Noise, Step-Up DC-DC Converters 0.7V TO 5.5V POUT 22µF L1 10µH REF MBR0520L MAX1700 MAX1701 OUT CLK/SEL P FB OUTPUT LX R LX Q D1 2x 100µF POUT 10Ω ONA S N 0.22µF OUT ONB 0.22µF R1 REF GND 0.22µF FB PGND ADJUSTABLE FIXED OUTPUT (GND) R2 1.3A CURRENT LIMIT PGND OSC Figure 2. Fixed or Adjustable Output (PWM mode). Figure 3. Simplified PWM Controller Block Diagram Table 1. Typical Available Output Current the output filter capacitor and load. As the energy stored in the inductor is depleted, the current ramps down and the output diode and synchronous rectifier turn off. Voltage across the load is regulated using either low-noise PWM or low-power operation, depending on the CLK/SEL pin setting (Table 2). NUMBER OF CELLS INPUT OUTPUT OUTPUT VOLTAGE (V) VOLTAGE (V) CURRENT (mA) 1 NiCd/NiMH 1.2 3.3 300 2 NiCd/NiMH 2.4 3.3 750 2 NiCd/NiMH 2.4 5.0 525 3 NiCd/NiMH or 1 Li-Ion 3.6 5.0 850 Table 2. Selecting the Operating Mode CLK/SEL MODE FEATURES 0 Low Power Low supply current 1 PWM Low noise, high output current External Clock (200kHz to 400kHz) Synchronized PWM Low noise, high output current Step-Up Converter The step-up switching DC-DC converter generates an adjustable output from 2.5V to 5.5V. During the first part of each cycle, the internal N-channel MOSFET switch is turned on. This allows current to ramp up in the inductor and store energy in a magnetic field. During the second part of each cycle, when the MOSFET is turned off, the voltage across the inductor reverses and forces current through the diode and synchronous rectifier to 10 Low-Noise PWM Operation When CLK/SEL is pulled high, the MAX1700/MAX1701 operate in a higher power, low-noise pulse-widthmodulation (PWM) mode. During PWM operation, they switch at a constant frequency (300kHz) and then modulate the MOSFET switch pulse width to control the power transferred per cycle and regulate the voltage across the load. In PWM mode the devices can output up to 800mA. Switching harmonics generated by fixedfrequency operation are consistent and easily filtered. See the Noise Spectrum Plot in the Typical Operating Characteristics. During PWM operation, each rising edge of the internal clock sets a flip-flop, which turns on the N-channel MOSFET switch (Figure 3). The switch is turned off when the sum of the voltage-error, slope compensation, and current-feedback signals trips a multi-input comparator and resets the flip-flop; the switch remains off for the rest of the cycle. When a change occurs in the output-voltage error signal into the comparator, it shifts the level to which the inductor current is allowed to ramp during each cycle and modulates the MOSFET switch pulse width. A second comparator enforces an inductor current limit of 1.6A max. ______________________________________________________________________________________ 1-Cell to 3-Cell, High-Power (1A), Low-Noise, Step-Up DC-DC Converters POUT Q R P ERROR COMPARATOR FB LX S Q N REF R 400mA CURRENT LIMIT Synchronous Rectifier The MAX1700/MAX1701 feature an internal 250mΩ, Pchannel synchronous rectifier to enhance efficiency. Synchronous rectification provides a 5% efficiency improvement over similar nonsynchronous boost regulators. In PWM mode, the synchronous rectifier is turned on during the second half of each switching cycle. In low-power mode, an internal comparator turns on the synchronous rectifier when the voltage at LX exceeds the boost-regulator output and then turns it off when the inductor current drops below 70mA. Low-Voltage Start-Up Oscillator PGND Figure 4. Controller Block Diagram in Low-Power PFM Mode Synchronized PWM Operation By applying an external clock to CLK/SEL, the MAX1700/MAX1701 can also be synchronized in PWM mode to a frequency between 200kHz and 400kHz. This allows the user to set the harmonics to avoid IF bands in wireless applications. The synchronous rectifier is also active during synchronized PWM operation. Low-Power PFM Operation Pulling CLK/SEL low places the MAX1700/MAX1701 in a low-power mode. During low-power mode, PFM operation regulates the output voltage by transferring a fixed amount of energy during each cycle and then modulating the switching frequency to control the power delivered to the output. The devices switch only as needed to service the load, resulting in the highest possible efficiency at light loads. Output current capability in PFM mode is 100mA. The output voltage is typically 1% higher than the output voltage in PWM mode. During PFM operation, the error comparator detects the output voltage falling out of regulation and sets a flipflop, turning on the N-channel MOSFET switch (Figure 4). When the inductor current ramps to the PFM mode current limit (400mA typical) and stores a fixed amount of energy, the current-sense comparator resets a flipflop. The flip-flop turns off the N-channel switch and turns on the P-channel synchronous rectifier. A second flip-flop, previously reset by the switch’s “on” signal, inhibits the error comparator from initiating another cycle until the energy stored in the inductor is transferred to the output filter capacitor and the synchronous The MAX1700/MAX1701 use a CMOS, low-voltage start-up oscillator for a 1.1V guaranteed minimum startup input voltage at +25°C. On start-up, the low-voltage oscillator switches the N-channel MOSFET until the output voltage reaches 2.15V. Above this level, the normal boost-converter feedback and control circuitry take over. Once the device is in regulation, it can operate down to a 0.7V input since internal power for the IC is bootstrapped from the output using the OUT pin. Do not apply full load until the output exceeds 2.4V. Table 3. On/Off Logic Control ONA ONB Status 0 0 On 0 1 Off 1 0 On 1 1 On Shutdown The MAX1700/MAX1701 shut down to reduce quiescent current to typically 3µA. During shutdown, the reference, low-battery comparator, gain block, and all feedback and control circuitry are off. The boost converter’s output drops to one Schottky diode drop below the input. Table 3 shows the control logic with ONA and ONB. Both inputs have trip points near 0.5V OUT with 0.15VOUT hysteresis. Low-Battery Comparator (MAX1701) The internal low-battery comparator has uncommitted inputs and an open-drain output (LBO) capable of sinking 1mA. To use it as a low-battery-detection comparator, connect the LBN input to the reference, and connect the LBP input to an external resistor divider ______________________________________________________________________________________ 11 MAX1700/MAX1701 rectifier current has ramped down to 70mA. This forces operation with a discontinuous inductor current. LOGIC HIGH D Q MAX1700/MAX1701 1-Cell to 3-Cell, High-Power (1A), Low-Noise, Step-Up DC-DC Converters 0.7V TO 5.5V POUT REF L1 MAX1701 D1 MAX1701 LBO POUT LBN CLK/SEL 10Ω ONA ONB 0.22µF R3 POK LBP R4 LBO LBN REF AO GND PGND FB AIN 10k R6 LBP OUT ARBITRARY VOLTAGE VOLTAGE MONITOR LOW-BATTERY MONITOR 0.22µF R5 LX GND BATTERY VOLTAGE R5 ARBITRARY VOLTAGE MONITOR Figure 7. Detecting Battery Voltages Below 1.25V (MAX1701) R6 OUTPUT 10Ω P Figure 5. Detecting Battery Voltage Above 1.25V C5 270k C3 0.22µF POUT OUT R3 LBN C4 POUT OUT MAX1701 R4 LBO MAX1701 LBO R3 LBP 0.22µF LBN GND Figure 6. Using the Low-Battery Comparator to Sense the Output Voltage (MAX1701) between the positive battery terminal and GND (Figure 5). The resistor values are then calculated as follows: R3 = R4(VTH/VLBN -1) where VTH is the desired input voltage trip threshold and VLBN = VREF = 1.25V. Since the input bias current into LBP is less than 20nA, R4 can be a large value (such as 270kΩ or less) without sacrificing accuracy. The inputs have a common-mode input range from 0.5V to 1.5V and an input-referred hysteresis of 15mV. The low-battery comparator can also be used to monitor the output voltage, as shown in Figure 6. To set the low-battery threshold to a voltage below the 1.25V reference, insert a resistor divider between REF 12 GND R4 REF 0.22µF LBP REF Figure 8. Using the Low-Battery Comparator for Load Control During Start-Up and LBN and connect the battery to the LBP input through a 10kΩ current-limiting resistor (Figure 7). The equation for setting the resistors for the low-battery threshold is then as follows: R5 = R6(VREF/VLBP -1) where VLBP is the desired voltage threshold. In Figures 5, 6, and 7, LBO goes low for a low-voltage input. The low-battery comparator can be used to check the output voltage or to control the load directly on POUT during start-up (Figure 8). Use the following equation to set the resistor values: R3 = R4(VOUTTH/VLBP - 1) where VOUTTH is the desired output-voltage trip point and VLBP is connected to the reference or 1.25V. ______________________________________________________________________________________ 1-Cell to 3-Cell, High-Power (1A), Low-Noise, Step-Up DC-DC Converters Gain Block (MAX1701) The MAX1701’s gain block can function as a third comparator or can be used to build a linear regulator using an external P-channel MOSFET pass device. The gainblock output is a single-stage transconductance amplifier that drives an open-drain N-channel MOSFET. Figure 9 shows the gain block used in a linear regulator. The output of an external P-channel pass element is compared to the internal reference. The difference is amplified and used to drive the gate of the pass element. Use a logic-level PFET such as the Fairchild ). If the PFET RDS(ON) is NDS336P (RDS(ON) = 270mΩ less than 250mΩ, the linear regulator output filter capacitance may need to be increased to above 47µF. Power-OK (MAX1701) The MAX1701 features a power-good comparator. This comparator’s open-drain output (POK) is pulled low when the output voltage falls to 10% below the regulation point. IN 20k 2x 100µF MAX1701 __________________Design Procedure P LX 47µF AO N Setting the Output Voltages Set the output voltage between 2.5V and 5.5V by connecting a resistor voltage-divider to FB from OUT to GND, as shown in Figure 2. The resistor values are then as follows: R1 = R2 (VOUT/VFB - 1) R5 AIN where VFB, the boost-regulator feedback setpoint, is 1.23V. Since the input bias current into FB is less than 20nA, R2 can have a large value (such as 270kΩ or less) without sacrificing accuracy. Connect the resistor voltage-divider as close to the IC as possible, within 0.2in. (5mm) of the FB pin. REF R6 Figure 9. Using Gain Block as a Linear Regulator Table 4. Component Suppliers SUPPLIER PHONE Inductor Selection FAX AVX USA: (803) 946-0690 (800) 282-4975 (803) 626-3123 Coilcraft USA: (847) 639-6400 (847) 639-1469 Matsuo USA: (714) 969-2491 (714) 960-6492 Motorola USA: (602) 303-5454 (602) 994-6430 Sanyo USA: (619) 661-6835 Japan: 81-7-2070-6306 (619) 661-1055 81-7-2070-1174 Sumida USA: (847) 956-0666 Japan: 81-3-3607-5111 (847) 956-0702 81-3-3607-5144 The MAX1700/MAX1701’s high switching frequency allows the use of a small surface-mount inductor. A 10µH inductor should have a saturation-current rating that exceeds the N-channel switch current limit of 1.6A. However, it is generally acceptable to bias the inductor current into saturation by as much as 20%, although this will slightly reduce efficiency. For high efficiency, choose an inductor with a high-frequency core material (such as ferrite) to reduce core losses. To minimize radiated noise, use a toroid, pot core, or shielded bobbin inductor. Connect the inductor from the battery to the LX pin as close to the IC as possible. See Table 4 for a list of component suppliers and Table 5 for suggested components. Table 5. Component Selection Guide PRODUCTION INDUCTORS CAPACITORS DIODES Surface Mount Sumida CDR63B, CD73, CDR73B, CD74B series Coilcraft DO1608, DO3308, DT3316 series Matsuo 267 series Sprague 595D series AVX TPS series Motorola MBR0520L Through Hole Sumida RCH654 series Sanyo OS-CON series Nichicon PL series 1N5817 ______________________________________________________________________________________ 13 MAX1700/MAX1701 Reference The MAX1700/MAX1701 have an internal 1.250V, 1% bandgap reference. Connect a 0.22µF bypass capacitor to GND within 0.2in. (5mm) of the REF pin. REF can source up to 50µA of external load current. MAX1700/MAX1701 1-Cell to 3-Cell, High-Power (1A), Low-Noise, Step-Up DC-DC Converters µC 270k LX MAX1701 ONB ON/OFF VDD OUT I/O ONA 0.1µF POUT MAX1700 I/O MAX8865/MAX8866 DUAL OR MAX8863/MAX8864 SINGLE LOW-DROPOUT LINEAR REGULATORS PA 270k µC Figure 10. Momentary Pushbutton On/Off Switch Output Diode Use a Schottky diode, such as a 1N5817, MBR0520L, or equivalent. The Schottky diode carries current during start-up, and in PFM mode after the synchronous rectifier turns off. Thus, its current rating only needs to be 500mA. Connect the diode between LX and POUT as close to the IC as possible. Do not use ordinary rectifier diodes since slow switching speeds and long reverse recovery times will compromise efficiency and load regulation. Input and Output Filter Capacitors Choose input and output filter capacitors that will service the input and output peak currents with acceptable voltage ripple. Choose input capacitors with working voltage ratings over the maximum input voltage, and output capacitors with working voltage ratings higher than the output. For full output, two 100µF, 100mΩ, low-ESR tantalum output filter capacitors are recommended. For loads below 250mA, a single 100µF output capacitor will suffice. The input filter capacitor (CIN) reduces peak currents drawn from the input source and reduces input switching noise. The input voltage source impedance determines the required size of the input capacitor. When operating directly from one or two NiCd cells placed close to the MAX1700/MAX1701, use a 22µF, low-ESR input filter capacitor. When operating from a power source placed farther away, or from higher impedance batteries such as alkaline or lithium cells, use one or two 100µF, 100mΩ, low-ESR tantalum capacitors. Sanyo OS-CON and Panasonic SP/CB-series ceramic capacitors offer the lowest ESR. Low-ESR tantalum capacitors are a good choice and generally offer a good tradeoff between price and performance. Do not 14 RADIO Figure 11. Typical Phone Application exceed the ripple current ratings of tantalum capacitors. Avoid most aluminum-electrolytic capacitors, since their ESR is often too high. Bypass Capacitors Two ceramic bypass capacitors are required for proper operation. Bypass REF with a 0.22µF capacitor to GND. Also connect a 0.22µF ceramic capacitor from OUT to GND. Each should be placed as close to their respective pins as possible, within 0.2in. (5mm) of the DC-DC converter IC. See Table 4 for suggested suppliers. __________Applications Information Push-On/Push-Off Control A momentary pushbutton switch can be used to turn the MAX1700/MAX1701 on and off. In Figure 10, ONA is pulled low and ONB is pulled high when the part is off. When the momentary switch is pressed, ONB is pulled low and the regulator turns on. The switch must be pressed long enough for the microcontroller to exit reset (200ms) and drive ONA high. A small capacitor is added to help debounce the switch. The controller issues a logic high to ONA, which holds the part on regardless of the switch state. To turn the regulator off, press the switch again, allowing the controller to read the switch status and pull ONA low. When the switch is released, ONB is pulled high. Use in a Typical Wireless Phone Application The MAX1700/MAX1701 are ideal for use in digital cordless and PCS phones. The power amplifier (PA) is connected directly to the boost-converter output for maximum voltage swing (Figure 11). Low-dropout linear regulators are used for post-regulation to generate ______________________________________________________________________________________ 1-Cell to 3-Cell, High-Power (1A), Low-Noise, Step-Up DC-DC Converters Designing a PC Board High switching frequencies and large peak currents make PC board layout an important part of design. Poor design can cause excessive EMI and groundbounce, both of which can cause instability or regulation errors by corrupting the voltage and current feedback signals. Power components (such as the inductor, converter IC, filter capacitors, and output diode) should be placed as close together as possible, and their traces should be kept short, direct, and wide. A separate low-noise ground plane containing the reference and signal grounds should only connect to the power-ground plane at one point. This minimizes the effect of powerground currents on the part. Consult the MAX1701 EV kit manual for a layout example. On multilayer boards, do not connect the ground pins of the power components using vias through an internal ground plane. Instead, place them close together and route them in a star-ground configuration using component-side copper. Then use vias to connect the star ground to the internal ground plane. Keep the voltage feedback network very close to the IC, within 0.2in. (5mm) of the FB pins. Keep noisy traces, such as from the LX pin, away from the voltage feedback networks. Separate them with grounded copper. Consult the MAX1700 evaluation kit for a full PC board example. Soft-Start To implement soft-start, set CLK/SEL low on power-up; this forces low-power operation and reduces the peak switching current to 550mA max. Once the circuit is in regulation and start-up transients have settled, CLK/SEL can be set high for full-power operation. Intermittent Supply/Battery Connections When boosting an input supply connected with a mechanical switch, or a battery connected with spring contacts, input power may sometimes be intermittent as a result of contact bounce. When operating in PFM mode with input voltages greater than 2.5V, restarting after such dropouts may initiate high current pulses that interfere with the MAX1700/MAX1701 internal MOSFET switch control. If contact or switch bounce is anticipated in the design, use one of the following solutions. 1) Connect a capacitor (CONB) from ONB to VIN, a 1MΩ resistor (RONB) from ONB to GND, and tie ONA to GND (Figure 12). This RC network differentiates fast input edges at VIN and momentarily holds the IC off until VIN settles. The appropriate value of CONB is 10-5 times the total output filter capacitance (COUT), so a COUT of 200µF results in CONB = 2nF. 2) Use the system microcontroller to hold the MAX1700/MAX1701 in shut down from the time when power is applied (or reapplied) until the output capacitance (COUT) has charged to at least the input voltage. Power-on reset times of tens of milliseconds accomplish this. 3) Ensure that the IC operates, or at least powers up, in PWM mode (CLK/SEL = high). Activate PFM mode only after the VOUT has settled and all of the system’s poweron reset flags are cleared. Pin Configurations (continued) TOP VIEW LBP 1 16 LBO LBN 2 15 POUT REF 3 14 OUT CLK/SEL 4 MAX1701 13 LX GND 5 12 PGND POK 6 11 FB ONB 7 10 AIN ONA 8 9 QSOP CONB 2nF LX 7 ONB RONB 1M OUT MAX1700 MAX1701 8 ONA POUT 13 14 COUT 200µF 15 AO Figure 12. Connecting CONB and RONB when Switch or Battery-Contact Bounce Is Anticipated ______________________________________________________________________________________ 15 MAX1700/MAX1701 low-noise power for DSP, control, and RF circuitry. Typically, RF phones spend most of their life in standby mode with only short periods in transmit/receive mode. During standby, maximize battery life by setting CLK/SEL = 0; this places the IC in low-power mode (for the lowest quiescent power consumption). Chip Information TRANSISTOR COUNT: 531 SUBSTRATE CONNECTED TO GND ________________________________________________________Package Information QSOP.EPS MAX1700/MAX1701 1-Cell to 3-Cell, High-Power (1A), Low-Noise, Step-Up DC-DC Converters 16 ______________________________________________________________________________________